Organic Electrosynthesis - Fundamentals and Applications of Organic Electrochemistry - page 248

ionic liquids up to a million times [67]. In
addition, because the polymers have
cycle-switching speeds as fast as 100 ms, they
can be used as electrochromic windows and
numeric displays. Furthermore, it was
demonstrated that polyaniline prepared in this
way is highly useful for electrochemical
actuators. A 10-mm length of 59-µm diameter
wet-spun polyaniline emeraldine base (EB)
fibre is treated with trifluoromethanesulfonic
(triflic) acid to form the corresponding
emeraldine salt (ES) fibre, which has high
conductivity of 300 S cm −1 . The fibre with ES
structure is reduced with two electrons at about
−0.4 V vs. Ag/Ag + in ionic liquid [bmim]BF 4 to
form leucoemeraldine (LE), and LE is oxidized
at about +0.8 V vs. Ag/Ag + to form original ES,
as shown in Figure 6.25 . Thus, by oxidation and
reduction, the cation of the ionic liquid,
[bmim], is expelled and incorporated,
respectively. The strain is therefore contractile
when the polymer is oxidized from the fully
reduced LE state to ES, and expansive upon
reduction ( Figure 6.25 ). In lifetime tests of the
fibre, both electroactivity and
electromechanical actuation continue without
significant decrease (<1%) in either stress or
strain for 10,000 redox cycles because
anhydrous ionic liquid is used as a solvent. The
π-conjugated polymer in an ionic liquid
electrolyte system is therefore highly promising
for electrochemical mechanical actuators.